CAMBRIDGE, Mass. — HORACE GREELEY, Napoleon Bonaparte and Cecil Rhodes may seem strange bedfellows, but they all agreed that territorial, political and economic size was critical to a country’s success. They wanted more land — in the West, in Europe or overseas. In 1904, Halford Mackinder, an Oxford geographer, told an august assemblage at the Royal Geographical Society that the country that controlled the Russian “heartland,” a frostbitten Central Asian steppe, would dominate “the world island” — the combined territory of Europe and North Asia — and in time come to rule the world. A centrally located piece of territory like the Russian plain, Mackinder argued, could be expanded West and East without the need for naval power.

As it turned out, Russia was then facing both war and revolution, and could not fully control the heartland, to say nothing of ruling the entire world. But Mackinder’s terms pointed to the critical role of territorial and economic size in the competition among nations.

Without quoting Mackinder, President Obama and Chancellor Angela Merkel of Germany have recently sought to form a huge free-trade zone that would join Europe with the United States in a new Transatlantic Trade and Investment Partnership, creating an economic power with nearly half of the world’s gross domestic product. On June 19, alongside Ms. Merkel in Berlin, Mr. Obama declared that Europe and the United States were the “engine of the global economy” and that they should “see ourselves as something bigger” in the global quest for freedom, justice and peace.

Of course, the joining of the two continents would increase trade and employment. It would facilitate Mr. Obama’s goal of doubling American exports and increasing investment and consumption. Ms. Merkel would smile as German cars and medical equipment poured into American markets, and Washington would return the favor with microprocessors, biotechnical devices and liquid natural gas. If the deal is concluded next year as planned, economists estimate the creation at least one million jobs over 10 years, and a 0.5 percent increase in G.D.P., on both sides of the Atlantic. The new pact would draw together 259 of the Fortune 500 companies. Investment flows and tourism would bubble to new heights.